Method for continuous tube producing



Jan. 12, 1965 s. o. s. STARK 3,165,035

METHOD FOR CONTINUOUS TUBE PRODUCING Filed Oct. 26. 1961 INVENTOR ATTORNEYS- United States Patent This invention relates to a method offorming from a flexible but relatively buckling-stiff web a continuoustube having a longitudinal seam parallel to the tube axis.

From e.g. the US. Patent No. 2,832,271 an apparatus is known forproducing a continuous tube of this type from a flat web of a flexiblebut relatively buckling-stiff material. In this apparatus the web isgradually converted from its fiat stage into tube form by means ofsubstantially external tube forming means, and its longi tudinal edgesare joined into a longitudinal seam parallel to the tube axis.

Since the web is presupposed to be relatively bucklingstifI" and thusscarcely elastic, a considerable forming length is required in order toconvert the web from fiat into tubular shape without inconvenient creaselines, cracks or ruptures. In order that tension dilferences owing todifferences in the generatrice lengths in different points along the webwidth be avoided an infinite forming length theoretically would berequired. Owing to the fact that the web material in spite of itsrelatively buckling-stiffness or springiness nevertheless has a certainlimited ability to absorb and equalize tension variations, theforminglength may be reduced to a finite value.

In several cases, however, a forming length of a practical finite valueis a definite drawback, since it requires a considerable space for theforming apparatus. The drawback is especially apparent for suchpackaging machines, in which the tube is supplied with filling materialthrough its trailing end and is flat pressed along narrow transversezones to divide it into filled and sealed packages. As far as thefilling operation is concerned, the tube must be produced insubstantially vertical position having its trailing end uppermost, whichmoreover also is apparent from the above mentioned US. patent. Thisgives rise to an essentially total height of the packaging machine withrequirements on corresponding ceiling height in the room, where saidmachine is located.

By the method in accordance with the invention a means to avoid theabove mentioned drawbacks is indicated. This means implies that the tubeforming course is divided into three phases, viz, two forming phaseswith a connecting web guiding phase. In the first forming phase, thus,the fiat Web is double folded substantially along its longitudinalcentral line with the web side corresponding to the inside of the tubeturned inwards. In the guiding phase the double folded Web is carriedover a pulley drum or a similar guiding surface having such asrelatively large bending radius that in relation to the longitudinaldirection of the web transverse crease lines or cracks in the webmaterial along the central web crease substantially are avoided. In thefinal forming phase the double folded Web is formed into a tube having asubstantially circular cross section at the same time as both of itslongitudinal edges are joined in a longitudinal seam parallel to thetube axis.

Because of this improved method, it is possible to double fold the webWhile the web is traveling upwardly from a supply roll and then toconvert the double-folded Web into a cylindrical form while the tube istraveling downwardly. Thus, the height of the forming apparatus whenforming a vertical tube may be considerably reduced in relation to theabove mentioned conventional tube forming method.

In the following the invention will be described in 3,1h5fi35 PatentedJan. 12, 1965 greater detail reference being made to the accompanyingdrawing, in a schematic perspective view illustrating the method inaccordance with the invention applied to the production of filled andsealed tetrahedron-shaped packages.

From a supply roll 1 a web 2 packaging material is rolled off, which webe.g. may consist of a relatively thick paper web, whose one side has acovering, relatively thinner coating layer of a heat-scalable plasticmaterial, e.g. polyethylene, while its other side has a still thinnercoating layer of wax or plastic material. The web 2 is first carriedover a web tension adjustiug,'spring loaded flap 3 to a guide roller 4in order thereafter to be carried under web positioning pulley roller 5parallel to roller 4 and against which the thicker coating layer of theweb 2. engages. From the pulley roller 5 the web 2 is carried upwardssubstantially vertically in doing which it is first gradually doublefolded, substantially around its longitudinal central line and carriedbetween two co-operating clamping rollers 6 and '7 having their mutuallyparallel axis substantially perpendicular to as well the longitudinaldirection of the web 2 as the pulley roller 5. In the space between theclamping rollers d and 7 the double folding of the web 2 is performed,and therefore the web 2 leaves this space in a flat, double folded stateand is carried up and over a pulley drum 8 located at a distance abovethe clamping rollers 6 and 7 and rotatable on an axis parallel with axisof rollers 6, '7. Between the pulley drum 8 and the space of theclamping rollers the double folded web 2' is guided laterally by meansof three peripherically grooved discs 9, l0 and 11 having their axissubstantially perpendicular to the side plane of the web and with theirperipherical grooves engage the respective longitudinal edges of thedouble folded web 2.

The pulley drum 8 has such a relatively large radius that in relation tothe longitudinal direction of the web transverse crease lines or cracksin the web material along the central web crease substantially areavoided. These crease lines or cracks are not only aestheticallydisfigurating for the final tube, but involve furthermore a risk forruptures in the web material, which ruptures could be fateful, if forinstance the tube should form the walls in a package intended forliquids.

From the pulley drum 8 the double folded web is carried substantiallyhorizontal to a similar pulley drum 12, whose axis is parallel to thefirst mentioned pulley drum 8. Over the second pulley drum 1?. the web 2is so guided that it leaves the drum 12 substantially verticallydownwards.

Immediately below the drum 12 the gradual forming of the double foldedweb 2 into the desired tube 13 thereafter follows. Encircling but notengaging against a substantially vertical filling pipe 14 the web 2 iscarried into a horizontal forming ring 15 having a shape correspondingto the desired cross sectional shape of the tube 13 to be formed at acorresponding level below the other pulley drum 12.

At some distance below the tube forming ring 15 there is a longitudinalsealing element 16 with an external joint pressure roller 17. Thesealing element 16 seals together thetwo overlapping edges of the web 2which have been brought together by the tube forming ring 15, and anexternal pressure roller 17 in cooperation with an internal pressureroller, not illustrated, located within the tube and supported by thefilling pipe 14 completes the longitudinal seam of the tube 13.

In the present case the sealing element 16 is suitably in a bracket i3by means of a projecting arm 19 from the filling pipe 14 between the webedges separated into a slot at this level. The supplying pipe 26 to thefilling pipe 14 is consequently also carried through the above mentionedslot.

For the downwards directed feeding of the continuously produced tube 13,but in the first place for dividing the tube 13 into filled and sealedpackages below the pressure roller 17 and in the extension of the tubethere are two yokes 21 and 22 along the tube axis and by means of guidebars 23 and 24, respectively, these yokes are displaceable in areciprocating manner, the one yoke 21 inside the other yoke 22. Theyokes 21 and 22 each support a pair of cooperating clamping jaws (notshown). The pairs of clamping jawsare arranged to flat press the tube l3along relatively narrow transverse zones in relation to the tube axisand by heating the inside of the plastic layer in these zones to dividethe tube 13 into filled and sealed packages. In the actual case bothpairs of clamping jaws are intended to flat-press and heat-seal the tube13 in mutually, substantially perpendicular planes in order to producetetrahedron-shaped packages. Furthermore each of the pairs of clampingjaws is provided with knife-means or the like being arranged by atransverse cut in each of the transverse sealing zones to separate thetransversely sealed finally closed package from the next-following one.

When functioning, both yokes 2i and 22 are driven by a common drive (notshown) also attending the operation of the pairs of clamping jaws. Theyokes 21 and 22 are moved in dependence on the drive in such a way thatone is carried to its uppermost point, while the other moves downwardswith its pair of clamping jaws in engagement with the tube 13 therebycarrying same, i.e. winding oil a corresponding length of the web 2.from the supply roll 1. When the downwards moving yoke has reached itslower position, the upwards moving yoke has reached its uppermostposition, by the drive and its pair of clamping jaws is brought intoengagement with the tube 13, while the pair of clamping jaws of thelower yoke releases same, etc.

In timed relationship to the tube feeding, i.e. the production ofpackages, the filling material is supplied to the inside of the tube 13to be formed through the supplying pipe 20 and the filling pipe 14. Thesupply of filling material can for instance be performed by means of acharging pump driven by the above mentioned drive or the like.

In order that the tube forming be effected substantially withoutstresses and independent of the tension variations induced by thesimultaneous tube feeding and package forming the pulley drum issuspended in one end of a bail 25 the other end of which is pivotableabout a pivot (not shown) parallel to the axis of the drum 12. Bycoupling means (not shown either) the bail 25 is connected to the driveof the apparatus in such a manner that the drum 12 will in timedrelationship to the intermittent downward tube feeding swing downwards adistance substantially corresponding to the advance stroke, thereafterto swing upwards again and thereby eiiect a corresponding advance of theweb 2 from the supply roll 1.

Thus, the invention makes possible a division of the tube formingoperation into two tube forming steps proper with an intermediate webguiding or deflecting step. For that reason the tube forming operationno longer need be carried out completely along the tube axis or theextension thereof but the first tube forming step may be transferred toanother part of the space, e.g. parallel to the other tube forming phasebut of opposite direction in relation thereto as described above andshown in the drawing.

I claim:

In the method of forming a continuous tube having a longitudinal seamparallel to the tube axis from a continuous web of flexible butrelatively buckling stiff material, the steps which comprise firstlymoving the web upwardly and simultaneously double folding the websubstantially along its longitudinal central line into a generallyfiattened state with the side of the web corresponding to the inside ofthe tube facing inwards, guiding said double folded web in saidflattened state through a path including a relatively large bendingradius to establish a movement of the Web in a downward direction,forming said downwardly moving double folded web into a tube ofsubstantially circular cross section and joining the oppositelongitudinal edges of said tube to establish a seam extendinglongitudinally of the tube axis.

References Cited in the file of this patent UNITED STATES PATENTS2,113,658 Lasko Apr. 12, 1938 2,237,119 Smith Apr. 1, 194i 2,326,931Dalton et a1 Aug. 17, 1943 2,346,044 Nadeau Apr. 4, l944 2,832,271Iarund Apr. 29, 1958

